The present invention relates to a concentrated polyol composition.
The invention also relates to its use for dispersing hydrocolloids such as cellulose and its derivatives, as well as for preparing pharmaceutical or cosmetological products, in particular such as toothpastes.
Toothpastes generally contain an abrasive agent, a wetting agent, water and a gelling agent used to impart a creamy or gel-type consistency and to form a support for all the other ingredients present in the toothpastes, such as flavourings, sweeteners and preserving agents.
The main function of the wetting agent is to maintain a certain level of humidity in the toothpaste when it is exposed to the open air, so as to prevent it from hardening and forming plugs in the orifice of the toothpaste tube.
The wetting agents usually used are glycerol and sorbitol as aqueous solutions, alone or as mixtures. Xylitol is sometimes used, but, since the process for producing it is more complex, it remains a more expensive product.
Consequently, for economic reasons, it is preferred to use sorbitol, which is found on the market in the form of syrups containing 70% solids.
In general, it is used in proportions from about 20 to about 70% of the weight of the toothpaste. It is moreover desirable for the sorbitol to be non-crystallizable, in order to ensure that it is stable before use and that the toothpastes are stable on storage.
As regards the gelling agents, hydrocolloids such as guar gum, guar derivatives, gum arabic, carrageenans, xanthans, methylcellulose, carboxymethylcellulose and hydroxyethylcellulose are generally used. They are used in proportions of from 0.1 to 5% by weight, depending on whether a paste or a gel is desired.
Sodium carboxymethylcellulose, more commonly referred to as CMC, is the gelling agent most commonly used in toothpastes.
During the preparation of toothpastes based on non-crystallizable sorbitol syrup containing 70% solids, the gelling agent is predispersed in the sorbitol syrup. This step is particularly critical since, although hydrophilic, the gelling agent has a tendency to form lumps and to aggregate. In certain cases, water penetrates these lumps very slowly and complete dispersion of the gelling agent is only reached after a considerable amount of time.
Certain manufacturers circumvent this problem by equipping themselves with very high shear mixers, but this equipment is very expensive.
Such is not the case when glycerol is selected as wetting agent, since the gelling agent disperses correctly in glycerol, which is anhydrous and thus does not solubilize it. Once water is added to the formulation, the gelling agent swells and disperses homogeneously to form a thick gel. This is the main advantage of glycerol over sorbitol.
However, many manufacturers are seeking to minimize their use of glycerol on account of its high and fluctuating cost, but also on account of its poor organoleptic performance.
However, as described above, there remains a problem to be solved for toothpaste formulators wishing to favour the use of sorbitol in replacement for glycerol.
One solution has been proposed in patent WO 97/48372 and consists in spraying polyol solutions onto hydrocolloid particles and then in drying the granules thus obtained on a fluidized bed. The polymer particles can then be incorporated into the toothpaste preparation without the formation of lumps. However, the fact remains that this additional step of preparation of the gelling agent further complicates the toothpaste formulation and is economically unacceptable.
Another solution, proposed in U.S. Pat. No. 4,883,537, consists in dispersing hydrocolloid in water, in the presence of an appreciable amount of potassium carbonate. It can easily be deduced that this solution is incompatible with use in toothpaste, on the one hand on account of the high alkalinity of potassium carbonate, and on the other hand on account of the supply of water imposed on the manufacturer.
To overcome the problems of aggregation of the gelling agents, it may be thought that it thus suffices to minimize the water content of the sorbitol syrups, since it is known, on the one hand, that when this water content is too high, lumps appear which are extremely difficult to remove, and, on the other hand, that when the water content of the dispersing medium is sufficiently low, there is no hydration or any anticipated swelling of the gelling agent, and thus no appearance of lumps.
However, the sorbitol syrups which are preferably used as wetting agents can exhibit concentration difficulties above a solids content of about 80%. This is because, when the water contained in such syrups is evaporated off, they become extremely viscous. Under these conditions, it is necessary to make use of sophisticated and thus expensive equipment. Furthermore, these very viscous products have the major drawback of no longer being pumpable, which makes them unsuitable for any industrial use, in particular with regard to the transportation, storage and processing of these syrups.
It has been proposed, in U.S. Pat. Nos. 3,651,936, 4,728,515, 4,671,961 and 4,671,967, to make use, for the preparation of food products such as chewing gums, of concentrated compositions based on coevaporated syrups of starch hydrolysates and of glycerol or of propylene glycol. The reason for this is that glycerol and propylene glycol lower the viscosity of starch hydrolysate syrups and make it easier to evaporate the water which these syrups contain. These concentrated compositions have a relatively low water content, for a glycerol content of at least 25% by weight. However, besides the drawback of its cost, glycerol by nature has an astringent and unpleasant taste which is generally detrimental to the organoleptic qualities of the final product. Similarly, patent WO 95/04107 has proposed dissolving polysaccharides in a mixture of sorbitol and glycerol. However, the presence of sorbitol in large proportions can entail risks of crystallization during storage. Furthermore, since the polysaccharide is present in small proportions (0.1%), this solution cannot be transposed to the preparation of toothpastes which generally contain from 1 to 5% gelling agent.
The aim of the invention is thus to overcome the drawbacks of the prior art and to provide a concentrated polyol composition containing sorbitol, which is better than the compositions which already exist in terms of the various practical requirements, i.e.:
which has a good capacity to disperse the gelling agents without forming lumps, and without necessarily using sophisticated equipment,
which has Theological properties such that it is easy to handle and to transport,
which is easy and economical to prepare,
which can be used in pharmaceutical or cosmetic products, in particular in toothpastes,
which is stable in itself and is capable of imparting sufficient stability on storage to the products into which it is incorporated, in particular with regard to the phenomena of crystallization during storage.
After detailed research, the Applicant has, to its merit, found that this aim can be achieved when the concentrated polyol composition has a selected water content and a specific carbohydrate profile.
Indeed, the Applicant has observed, surprisingly and unexpectedly, that a new phenomenon occurs, at high solids contents, during the dispersion of the gelling agents: in a first stage, the gelling agent disperses easily as expected, but, in a second stage, it absorbs the water present. This is equivalent to a substantial increase in the solids content of the medium, with, consequently, crystallization of the polyols, which is reflected in setting of the entire mixture to a solid.
Thus, unexpectedly, and as will moreover be demonstrated by examples, only a precise water content range in the polyol composition in fact makes it possible to disperse a gelling agent appropriately.
Above 17% water in the said composition, the gelling agent forms lumps in the preparation, and below 10% water, rapid setting of the mixture to a solid is observed after the gelling agent is added.
Advantageously, the water content should be between 12 and 16% in order to best avoid the problems mentioned above.
It was already known practice, in patent AU 642,177 of which the Applicant is the proprietor, to concentrate maltitol and xylitol syrups to water contents of 7 to 10%. However, the high content of hydrogenated disaccharides in these syrups, which are intended for food use, entails a high syrup viscosity. Moreover, these syrups contain virtually no sorbitol and do not necessarily satisfy the economic and functional requirements of manufacturers of pharmaceutical or cosmetological preparations, and in particular toothpaste manufacturers.
Other concentrated maltitol syrups have also been described in patent EP 0,072,080 for the preparation of gels, using very small amounts of carboxymethylcellulose.
These syrups, which are very rich in molecules with a degree of polymerization of 2 or more, are very viscous. Indeed, it is known that the viscosity is correlated with the molecular weight of the polyols contained in these syrups.
Viscous xylitol compositions are also known, which are described in U.S. Pat. No. 5,728,225, of which the Applicant is also the proprietor. These sorbitol-free compositions are of unsuitable viscosity.
Thus, the problem which is posed, in order to concentrate sorbitol syrups, relates to the stability and pumpability of the resulting compositions, the solids content of which is adjusted for satisfactory dispersibility of the gelling agents, these three criteria having never been combined in the prior art.
The Applicant has thus demonstrated that the stability and pumpability criteria can be satisfied when the polyol compositions, with a solids content which is adjusted for the dispersibility criterion, has a very specific carbohydrate profile.
The invention thus relates, firstly, to a concentrated polyol composition, characterized in that its water content is from 10 to 17%, preferably between 12 and 16%, and in that it comprises:
from 35 to 90% of hydrogenated monosaccharides including at least 30% of sorbitol,
from 0 to 45% of hydrogenated disaccharides, these percentages being expressed as dry weight relative to the dry weight of all of the saccharides contained in the said composition.
Preferably, this composition has a hydrogenated monosaccharides content of between 40 and 90% including at least 35% of sorbitol, and a hydrogenated disaccharides content of between 0 and 35%.
Even more preferably, it has a hydrogenated monosaccharides content of between 60 and 90% including at least 50% of sorbitol, and a hydrogenated disaccharides content of between 2 and 35%.
In point of fact, the Applicant has demonstrated, in the course of lengthy research studies, that by selecting this specific range of water contents, combined with this specific carbohydrate profile, polyol compositions according to the invention which are entirely suitable for the easy dispersion of hydrocolloids are obtained.
For the purposes of the present invention, the term xe2x80x9chydrogenated monosaccharidexe2x80x9d is intended to refer to a product preferably chosen from the group comprising sorbitol, mannitol, xylitol, arabitol, iditol and ribitol, and mixtures thereof.
Preferably, the hydrogenated monosaccharide is chosen from sorbitol and mannitol and any mixtures thereof.
The term xe2x80x9chydrogenated disaccharidexe2x80x9d is intended to refer to a product preferably chosen from the group comprising maltitol, lactitol, glucosido-1,6-mannitol, isomaltitol and cellobiitol, and any mixtures thereof.
Preferably, the hydrogenated disaccharide consists of maltitol. The composition according to the invention can also contain other hydrogenated saccharides such as, in particular, hydrogenated oligo- and polysaccharides. In particular, contents of from 10 to 19% by weight of polysaccharides whose degree of polymerization is greater than or equal to 3 are entirely suitable.
Besides the hydrogenated saccharides as described, this composition can also comprise conventional additives for pharmaceutical or cosmetic products, such as, for example, polishing materials, thickeners, surfactants, fluoro compounds, flavourings, sweeteners, dyes, bleaching agents, preserving agents or silicones.
According to an advantageous embodiment of the composition in accordance with the invention, it has a viscosity, measured at 45xc2x0 C., of less than 10,000 mPaxc2x7s, preferably less than 5000 mPaxc2x7s and even more preferably between 500 and 4500 mPaxc2x7s.
The reason for this is that only those compositions with such viscosities can generally be considered as pumpable, without any problem of overheating of the industrial pumps.
As regards measuring the viscosity, this is carried out using an Ares-type rheometer sold by the company Rheometric Scientific (US).
This rheometer is equipped with a cone-plate type measuring system and a thermostatic system.
The test solutions are deposited on a thermostatically-regulated movable plate. The shear resistance of the product between the cone and the rotating plate is measured at a given temperature.
The results are expressed in mPaxc2x7s.
It is important to express the viscosity each time as a function of the temperature at which it was measured, given that it is directly dependent thereon.
According to another variant, the composition in accordance with the invention is at a temperature above dispersion of gelling agents, but it is also particularly advantageous for toothpaste users and, especially, manufacturers who carry out their preparations under hot conditions. The reason for this is that the delivery of a hot polyol composition enables the users to dispense with an additional heating step.
Thus, the composition in accordance with the invention, at a temperature of between 30 and 55xc2x0 C., is particularly advantageous.
To prepare the composition in accordance with the invention, a syrup can be prepared from specific polyols in the state of powder or liquids or specific saccharide compositions can be hydrogenated, followed by evaporation of the water contained in the compositions thus prepared until a water content of between 10 and 17% by weight is reached. This evaporation step can be carried out using conventional devices, among which mention may be made of those sold under the brand name xe2x80x9cParavapxe2x80x9d by the company APV Equipment Incorporated of Tonowanda N.Y.
A composition in accordance with the invention which also has a very low reducing-sugar content can be prepared, this composition being stable to alkalis, which will allow it to be used in particular in toothpastes containing basic compounds.
This composition, commonly classed as xe2x80x9cunsweetenedxe2x80x9d by those skilled in the art, has a reducing-sugar content generally of less than 1000 ppm and preferably less than 500 ppm.
According to another embodiment, the composition in accordance with the invention can contain glycerol in small proportions, i.e. not more than 24% by weight of the said composition, so as to further improve the fluidity of the composition, if necessary. Glycerol contents of about 5 to 10% by weight may be suitable.
Next, to disperse the hydrocolloids, in particular such as cellulose and its derivatives, a general, novel and inventive means is now available, consisting of concentrated, selected polyol compositions as described above.
These compositions can thus be used easily in the preparation of toothpastes, and in many pharmaceutical or cosmetic preparations such as syrups, gels, creams and mouthwashes. They can also be used in various chemical or agrochemical industries.
The compositions in accordance with the invention have other advantages in the industrial sector, namely reducing the transportation costs by reducing the amount of water to be transported, reducing the volumes to be stored, and reducing the risks of microbial contamination.
The implementation time is also reduced, on account of the optimization of the debubbling operations associated with a reduced presence of water, as well as by improving the dispersion time of the hydrocolloids of lower viscosity.